Subscribers to online services have virtually on-demand access to news, weather, financial, sports, and entertainment services as well as the ability to transmit electronic messages and to participate in online discussion groups. For example, subscribers of online service providers such as America Online or CompuServe may view and retrieve information on a wide variety of topics from repositories located throughout the world. Subscribers may perceive online content in a variety of ways. For example, a subscriber may read a document, view an image, or listen to a song while online.